Chapter 6: A Tour of the Cell
 Overview: The Fundamental Units of Life
• All organisms are ___________________________
• The cell is the simplest collection of matter ____________________
• Cell _______________ is correlated to cellular __________________
• ____________________ by their ______________________________
 Concept 6.1: To study cells, biologists use microscopes and the tools of biochemistry
• Though usually _____________________ by the unaided eye, cells can be complex
• Microscopy:
– Scientists use microscopes to visualize cells too small to see with the naked
eye
– In a ________________________ visible light passes through a specimen and
then through glass lenses, which magnify the image
• The quality of an image depends on
– ________________, the ratio of an object’s image size to its real size
– ________________, the measure of the clarity of the image, or the minimum
distance of two distinguishable points
– ________________, visible differences in parts of the sample
• LMs can magnify effectively to about _________________________ of the actual
specimen
• Various techniques enhance contrast and enable cell components to be stained or
labeled
• Most subcellular structures, including _________________ (membrane-enclosed
compartments), are ____________________________________
• Two basic types of ___________________________ are used to study subcellular
structures
– ___________________________________ focus a beam of electrons onto the
surface of a specimen, providing images that look 3-D
– ____________________________________ focus a beam of electrons through
a specimen
– TEMs are used mainly to study the __________________________
• Cell Fractionation
– __________________________ takes cells apart and separates the major
organelles from one another
• _______________ fractionate cells into their component parts
• Cell fractionation enables scientists to ___________________
__________________of organelles
• _________________ and _______________ help correlate cell function
with structure
 Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their
functions
• The basic structural and functional unit of every organism is one of two types of cells:
__________________________________
• Only organisms of the domains ________________________ consist of
____________________________
• ______________________________ all consist of ___________________
• Comparing Prokaryotic and Eukaryotic Cells
– Basic features of ________________:
• Plasma membrane
• Semifluid substance called ________________
• _________________________ (carry genes)
• ______________________ (make proteins)
– ____________________ are characterized by having:
• _____________________
• DNA in an unbound region called the ________________
• ____________________________ organelles
• _____________________ bound by the plasma membrane
– ________________________ are characterized by having:
• DNA in a _________________ that is bounded by a membranous
nuclear envelope
• _________________________ organelles
• _________________________ in the region between the plasma
membrane and nucleus
– Eukaryotic cells are generally ________________ than prokaryotic cells
– The _______________________ is a selective barrier that allows sufficient
passage of ______________________________ to service the
________________ of every cell
– The general structure of a biological membrane is a ______________
___________________
– The logistics of carrying out cellular metabolism sets ____________
____________________
– The __________________________________ of a cell is critical
– As the surface area increases by a factor of _____, the volume increases by a
factor of ______
– ________________ have a ________________ surface area relative to volume
• A Panoramic View of the Eukaryotic Cell
– A eukaryotic cell has_____________________ that partition the cell into
___________________
– Plant and animal cells have most of the same organelles (see diagrams)
 Concept 6.3: The eukaryotic cell’s genetic instructions are housed in the nucleus and
carried out by the ribosomes
• The__________________________________________ in a eukaryotic cell
– _____________ use the information from the DNA to ____________
• The _____________ is usually the ________________________ organelle
• The ________________________ encloses the nucleus, separating it from the
cytoplasm
• The nuclear membrane is a _______________________; each membrane consists of
a lipid bilayer
– _________ regulate the entry and exit of molecules from the nucleus
– The ________________ of the nucleus is maintained by the
__________________, which is composed of protein
– In the nucleus, DNA and proteins form genetic material called
____________________
– Chromatin condenses to form discrete ______________________
– The ________________ is located _________________________ and is the
site of ___________________________________
• Ribosomes: Protein Factories
– ______________are particles made of ________________________
– Ribosomes ________________________________ in two locations:
• In the ____________________ (free ribosomes)
• On the _____________________________________________
___________ (bound ribosomes)
 Concept 6.4: The endomembrane system regulates protein traffic and performs
metabolic functions in the cell
• Components of the ______________________________:
– _________________________
– _________________________
– _________________________
– _________________________
– _________________________
– _________________________
• These components are either continuous or connected via transfer by
________________________
• The Endoplasmic Reticulum: Biosynthetic Factory
– The ______________________________ accounts for more than half of the
total membrane in many eukaryotic cells
– The ER membrane is _________________ with the nuclear envelope
– There are two distinct regions of ER:
• ____________________, which lacks
ribosomes
• ____________________, with ribosomes
studding its surface
– Functions of the Smooth and Rough ER
• The __________________
o Synthesizes lipids (oils, phospholipids,
and steroids)
o Metabolizes carbohydrates
o Detoxifies poison (done by the smooth ER in liver cells)
o Stores calcium (in smooth ER of muscle cells)
• _____________________
o Has bound ribosomes, which secrete _________________
(proteins covalently bonded to carbohydrates)
o Distributes _________________________, proteins surrounded
by membranes
o Is a membrane factory for the cell
• The Golgi Apparatus: Shipping and Receiving Center
– The ______________________ consists of
membranous sacs called cisternae
– Functions of the Golgi apparatus:
• _____________________ of the ER
• _________________ certain
______________________
• ____________________ materials into
transport vesicles
• Lysosomes: Digestive Compartments
– A ___________________ contains hydrolytic enzymes that can
_____________________________
– Lysosomal enzymes can ____________________________________
________________________________________
• These enzymes work best in the acidic environment inside the
lysosome.
– Some cells can engulf other cells by _______________; this forms a
_______________________
• A _________________________________________ and digests the
molecules
– Lysosomes also can recycle the cell’s own organelles and macromolecules, a
process called ____________________
• Vacuoles: Diverse Maintenance Compartments
– A plant cell or fungal cell may have one or several
____________________
• _________________ are formed by
phagocytosis
• ___________________, found in many
freshwater protists, pump excess water out of
cells
• ______________________, found in many
mature plant cells, hold organic compounds and water. It develops from
the joining of smaller vacuoles formed from the ER and Golgi. This
makes it part of the endomembrane system.
• The Endomembrane System : A Review
– The endomembrane system is a complex and
dynamic player in the
__________________________________
 Concept 6.5: Mitochondria and chloroplasts change energy from one form to
another
• ____________________ are the sites of cellular respiration, a metabolic process that
generates ATP.
• ____________________, found in plants and algae, are the sites of photosynthesis
• ____________________ are oxidative organelles
• Mitochondria and chloroplasts
– Are _____ part of the endomembrane system
– Have a _______________________
– Have proteins made by ______________________
– _____________________________
• Mitochondria: Chemical Energy Conversion
– Mitochondria are in nearly ____________________
– They have a smooth outer membrane and an inner
membrane folded into _____________
– The inner membrane creates two compartments:
intermembrane space and mitochondrial matrix
– Some metabolic steps of cellular respiration are
________________ in the mitochondrial matrix
– Cristae ____________________________ for
enzymes that synthesize ATP
• Chloroplasts: Capture of Light Energy
– The chloroplast is a member of a family of organelles called _______
– Chloroplasts contain the green pigment ______________, as well as enzymes
and other molecules that function in photosynthesis
– Chloroplasts are found in leaves and other
____________________________________
– Chloroplast structure includes:
• _____________, membranous sacs, stacked to
form a __________
• ______________, the internal fluid
• Peroxisomes: Oxidation
– __________________ are specialized metabolic compartments bounded by a
_____________________
– Peroxisomes produce _________________ and convert it to ______
– Oxygen is used to break down different types of molecules
 Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and
activities in the cell
• The ________________ is a network of fibers extending throughout the cytoplasm
• It organizes the cell’s structures and activities, anchoring many organelles
• It is composed of three types of molecular structures:
– ______________________
– ______________________
– ______________________
• Roles of the Cytoskeleton: Support, Motility, and Regulation
– The cytoskeleton helps to _______________ and
_________________________
– It interacts with __________________ to produce _____________
– Inside the cell, vesicles can travel along “______________” provided by the
cytoskeleton
– Recent evidence suggests that the cytoskeleton _________________
_________________
• Components of the Cytoskeleton
– Three main types of fibers make up the cytoskeleton:
• __________________ are the thickest of the three components of the
cytoskeleton
• __________________, also called actin filaments, are the thinnest
components
• ________________________ are fibers with diameters in a middle
range
– Microtubules
• __________________ are hollow rods about 25 nm in diameter and
about 200 nm to 25 microns long
• Functions of microtubules:
o ______________________________
o _______________________________
o ___________________________________________
– Centrosomes and Centrioles
• In many cells, microtubules grow out from a _______________ near the
nucleus
• The centrosome is a
“______________________________”
• In animal cells, the centrosome has a pair of
_________________, each with nine triplets
of microtubules arranged in a ring
• Cilia and Flagella
– Microtubules control the beating of ______________________, locomotor
appendages of some cells
– Cilia and flagella differ in their beating patterns
• Flagella undulate
• Cilia function like oars of a boat
– Cilia and flagella share a common __________________:
• A core of microtubules sheathed by the plasma membrane
• A ______________________that anchors the cilium or
flagellum
• A motor protein called _____________, which drives the
bending movements of a cilium or flagellum
– How dynein “_____________” moves flagella and cilia:
• Dynein arms alternately grab, move, and release the outer microtubules
• Protein ______________________________
• Forces exerted by dynein arms cause doublets to ___________, bending
the cilium or flagellum
– Microfilaments (Actin Filaments)
• __________________ are solid rods about 7 nm in diameter, built as a
twisted double chain of ______________ (a globular protein)
• The structural role of microfilaments is to bear tension, resisting
_______________________________
• They form a 3-D network called the ____________ just inside the plasma
membrane to help support the cell’s shape
• Bundles of microfilaments make up the core of
___________________________________
• Microfilaments that function in cellular motility contain the protein
_____________ in addition to actin
• In muscle cells, thousands of actin filaments are arranged
_______________________________
• Thicker filaments composed of myosin interdigitate with the thinner actin
fibers
• Localized contraction brought about by actin and myosin also drives
amoeboid movement
o ________________ (cellular extensions) extend and contract through
the reversible assembly and contraction of actin subunits into
microfilaments
o __________________________ is a circular flow of cytoplasm within
cells
o This streaming speeds distribution of materials in the cell
o In plant cells, actin-myosin interactions and sol-gel transformations
drive cytoplasmic streaming
– Intermediate Filaments
• ______________ _____range in diameter from 8–12 nanometers,
larger than microfilaments but smaller than microtubules
• They support __________________________________________
• Intermediate filaments are _______________________
cytoskeleton fixtures than the other two classes
 Concept 6.7: Extracellular components and connections between cells help coordinate
cellular activities
• Most cells __________________________ materials that are external to the plasma
membrane
• These extracellular structures include:
– ________________________________________
– ________________________________________
– ________________________________________
• Cell Walls of Plants
– The ___________________ is an extracellular structure that distinguishes
plant cells from animal cells
– Prokaryotes, fungi, and some protists also have cell walls
– The cell wall protects the plant cell, maintains its shape, and prevents
excessive uptake of water
– Plant cell walls are made of _________________ embedded in other
polysaccharides and protein
– Plant cell walls may have multiple layers:
• ______________________: relatively thin and
flexible
• ______________________: thin layer between
primary walls of adjacent cells
• ______________________ (in some cells): added
between the plasma membrane and the primary
cell wall
– ____________________ are channels between
adjacent plant cells
• The Extracellular Matrix (ECM) of Animal Cells
– Animal cells lack cell walls but are
covered by an elaborate
_____________________________
– The ECM is made up of glycoproteins
such as collagen, proteoglycans, and
fibronectin
– ECM proteins bind to receptor proteins in
the plasma membrane called
_______________
– Functions of the ECM:
• ______________
• ______________
• ______________
• ______________
• Intercellular Junctions
– Neighboring cells in tissues, organs, or organ systems often adhere, interact,
and communicate through __________________________
– ________________________ facilitate this contact
– There are several types of intercellular junctions
• ______________________
• ______________________
• ______________________
• _______________________
– Plasmodesmata are channels that perforate plant cell walls.
• Through plasmodesmata, water and small solutes can pass from cell to
cell
– Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells
• At ___________________, membranes of
neighboring cells are pressed together,
preventing leakage of extracellular fluid (connect
skin cells)
• __________________ (anchoring junctions)
fasten cells together into strong sheets (connect
muscle cells)
• __________________ (communicating junctions)
provide cytoplasmic channels between adjacent
cells
The Cell: A Living Unit Greater Than the Sum of Its Parts
• Cells rely on the integration of structures and organelles in order to function
• For example, a macrophage’s ability to destroy bacteria involves the whole cell,
coordinating components such as the cytoskeleton, lysosomes, and plasma
membrane
You should now be able to:
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Distinguish between the following pairs of terms: magnification and resolution; prokaryotic and eukaryotic cell; free and bound
ribosomes; smooth and rough ER
Describe the structure and function of the components of the endomembrane system
Briefly explain the role of mitochondria, chloroplasts, and peroxisomes
Describe the functions of the cytoskeleton
Compare the structure and functions of microtubules, microfilaments, and intermediate filaments
Explain how the ultrastructure of cilia and flagella relate to their functions
Describe the structure of a plant cell wall
Describe the structure and roles of the extracellular matrix in animal cells
Describe four different intercellular junctions